The cellular mechanisms by which FFA arising from lipolysis within adipocytes exit these cells to enter the circulation are unknown. It has been suggested that FFA are transported within adipocytes sequestered within pinocytotic microvesicles and that this intracellular movement may participate in FFA mobilization. To test this proposal, the adipocyte cytoplasmic microtubular assembly, which mediates intracellular movements in other cells, will be disrupted with colchicine, vinca alkaloids, and podophyllin toxin and the consequences to FFA mobilization studied. If cytoplasmic microtubules participate in the outward movement of FFA from adipocytes, then destruction of microtubules should hinder this process. Because many cell processes which are dependent upon microtubules also exhibit a requirement for calcium ion, studies will be carried out to determine the dependence of FFA mobilization upon extracellular calcium. Assuming some calcium dependence is revealed, studies to evaluate the role of calcium influx and/or efflux into adipocytes will be implemented.